Beta-Sialon Phosphor Aspect Ratio Control
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Solution Overview
Problem
Conventional β-sialon phosphors have insufficient fluorescence intensity and are difficult to produce with a small aspect ratio, making them unsuitable for applications requiring high brightness and efficient light emission with near-ultraviolet to blue light excitation.
Innovation Solution
A β-sialon phosphor powder with a β-type Si3N4 crystal structure and a specific composition (Si6-zAlzOzN8-z:Eux) is produced using α-type silicon nitride with a large particle diameter and a low aspect ratio, followed by a firing process in a nitrogen atmosphere and subsequent acid washing and heat treatment to enhance fluorescence intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional β-sialon phosphor is used, then the phosphor can be produced, but the fluorescence intensity is insufficient
Solution Approach 1:
The patent changes the particle shape parameter (aspect ratio) of β-sialon phosphor from conventional acicular forms (aspect ratio > 2) to particles with aspect ratio of 2 or less. This parameter change in particle morphology directly improves fluorescence intensity and brightness by reducing light scattering and enhancing light absorption efficiency.
2Shape
If β-sialon phosphor is produced by conventional methods, then the phosphor can be synthesized, but the aspect ratio is large (acicular shape)
Solution Approach 1:
The patent applies preliminary action by performing acid washing treatment on the β-sialon phosphor particles after synthesis. This treatment removes glassy phases and surface impurities that contribute to acicular shape formation, enabling transformation to particles with smaller aspect ratio (≤2) and improving manufacturability of the desired shape.
3Illumination intensity
If the aspect ratio is reduced to improve fluorescence, then the particle shape changes, but the production process becomes more complex
Solution Approach 1:
The patent employs parameter changes by adjusting the acid washing conditions (acid type, concentration, temperature, time) to control the aspect ratio of β-sialon particles. By optimizing these parameters, the process achieves particles with aspect ratio ≤2 and high fluorescence intensity while maintaining reasonable production complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting β-sialon phosphor powder exhibits high fluorescence intensity and a small aspect ratio, suitable for applications like fluorescent displays, field emission displays, and light emitting diodes, with improved light absorption and reduced scattering, leading to enhanced brightness and efficiency.
Implementation Method 1
a phosphor capable of strongly emitting light with this excitation wavelength is demanded. The green light emitting β-sialon phosphor also requires a green fluorescence strongly emitting with the above-described excitation wavelength range.
Implementation Method 2
a washing treatment in a solution containing an acid is preferably applied after the firing.
Implementation Method 3
after the firing, a heat treatment is preferably performed within a temperature range of 300 to 1,000° C. in an atmosphere containing one member or two or more members selected from nitrogen, ammonia and hydrogen.
Data Source
AI summary
A β-sialon phosphor particle in which Eu (europium) is solid-soluted in a crystal having a β-type Si3N4 crystal structure, wherein the median diameter (D50) in the particle size distribution curve of the primary particle is from 3.0 to 10 μm and the aspect ratio is less than 1.5.